update index links to include 'post' directory (#1666)

* update index links to include 'post' directory

* rebuild github pages site

* document how to develop documentation

* build, not serve

dev_docs/developer_guidelines.md

@@ -151,3 +151,18 @@ If you would like to run the smoke tests against a hot-reloaded version of the c
 - You can also install/launch the server side code from npm scrips (requires python3.6 with virtualenv) with the `scripts/backend_dev` script.
 
 - Check out [e2e Tests](e2e_tests.md) for more details
+
+## Doc changes
+
+To evaluate changes to documentation in `cellxgene/docs`, you must install [jekyll](https://jekyllrb.com/docs/installation/), then run:
+
+```bash
+cd docs
+bundle install
+bundle exec jekyll serve
+```
+
+If changes look good, run the following, then commit and push: 
+```bash
+bundle exec jekyll build
+```